Police in Chicago have revealed that a 15-year-old girl was sexually assaulted by several young men while the attack streamed on Facebook Live. The incident was viewed by some 40 people, none of whom reported it to the authorities.

The attack on Deahvion Austin, which was reportedly carried out by five or six teenage boys or young men, was streamed live on the social media site.

However, police were oblivious to it until the girl’s mother approached Police Superintendent Eddie Johnson in the Lawndale neighborhood of the city’s West Side on Monday, according to police spokesman Anthony Guglielmi.

She told him that her daughter had been missing since leaving home to go to the store on Sunday, and showed him screenshots of the alleged assault, AP reported.

The teen’s mother, Stacey Elkins, learned of the video from the girl’s uncle, who came across it online.

“I just want her home,” Elkins said Monday, as quoted by WGN Chicago. “I just want to make sure she’s OK because I know she’s probably scared and embarrassed. I just want her back home.”

Johnson immediately ordered detectives to investigate the attack, and the police department asked Facebook to remove the video, which it did.

The girl was later reunited with her family after being located by detectives, Guglielmi tweeted Tuesday, adding that authorities are conducting interviews.

LOCATED: Deahvion Austin was found by 10th district officers. She is now at the Area with her mother & detectives are conducting interviews. https://t.co/1UEAiL0JYn

The spokesman said Johnson was “visibly upset” after he watched the video, due to its content and the fact that “40 or so live viewers” failed to call the authorities.

“What’s even more disturbing – more than the fact that they did this – (is that) there were so many people that saw this and they didn’t pick up the phone and dial 911,” Johnson told WGN on Monday. “That’s just not right and [we’re] working on it and trying to bring it to a successful resolution.”

The incident comes less than three months after a Chicago teen with mental disabilities was tortured in a Facebook Live video. The footage showed four African-American suspects cutting and repeatedly hitting the victim while shouting “F* Donald Trump! F* white people!”

Suicides have also become a rising problem on Facebook Live, with the social media site’s founder and CEO Mark Zuckerberg vowing to find ways to prevent such tragedies in a letter to users last month.

“There have been terribly tragic events — like suicides, some live streamed — that perhaps could have been prevented if someone had realized what was happening and reported them sooner,” he wrote at the time.

Facebook began airing its Live feature last year. Since then, it has been promoting the tool on the site, calling it a “fun, powerful way to connect with your followers and create new ones along the way.”